Regulation of rat liver guanine amino hydrolase by GTP

Josan, V.; Krishnan, P. S.

doi:10.1016/0006-291x(68)90474-9

Cited by 8 publications

(2 citation statements)

References 4 publications

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“…As briefly communicated (Josan & Krishnan, 1968; Sree Kumar & Krishnan, 1970b;Sitaramayya & Krishnan, 1970), guanine deaminase activity can be modulated by positive and negative effectors. K. S. K. is grateful to the University Grants Commission and A. S. to the Council of Scientific and Industrial Research, New Delhi, for the award of research fellowships.…”

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confidence: 98%

Guanine deaminase in rat liver and mouse liver and brain

Kumar

Sitaramayya

Krishnan

1972

Biochemical Journal

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1. The guanine deaminase in rat liver supernatant preparations was resolved into two fractions, A and B, on DEAE-cellulose columns. The two differed in electrophoretic mobility and in various properties. The most noteworthy distinction between A and B components was that the enzyme A activity showed a sigmoid dependence on substrate concentration whereas the enzyme B showed classical Michaelis-Menten kinetics. The K(m) value of enzyme A for guanine was 5.3mum and that of enzyme B 20mum. 2. The entire guanine deaminase activity of mouse liver was contained in the 15000g supernatant of iso-osmotic homogenates. 3. A reinvestigation of the behaviour of rat brain 15000g supernatant guanine deaminase isoenzymes revealed that one enzyme had sigmoidal kinetics and the other enzyme showed a hyperbolic response. 4. Of the guanine deaminase in mouse brain iso-osmotic sucrose homogenate 80% was recovered in the 15000g supernatant and the rest from the particles. The supernatant guanine deaminase was resolvable into two fractions on DEAE-cellulose columns. One enzyme showed sigmoidal kinetics whereas the other showed a hyperbolic response to increasing substrate concentration; the K(m) values for the reaction with guanine were respectively 5 and 66mum. 5. The particulate fractions of mouse liver and brain were devoid of any overt inhibitory activity.

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Guanine deaminase in rat liver and mouse liver and brain

Kumar

Sitaramayya

Krishnan

1972

Biochemical Journal

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“…Guanine is deaminated to xanthine by guanase which has the highest activity in mammalian brain and hepatic tissues. The enzyme appears to be regulated by a protein inhibitor and GTP [18,19]. Hypoxanthine and xanthine are converted to uric acid by xanthine oxidase located primarily in the liver and jejunum of mammals.…”

Section: Uric Acidmentioning

confidence: 99%

Purine Ribonucleotide Catabolism: Clinical and Biochemical Significance

Fox¹

1974

Ann Nutr Metab

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Purine ribonucleotides are degraded to uric acid by a complexly regulated metabolic pathway. Abrupt lowering of intracellular ATP, a physiological inhibitor of this pathway at normal concentrations, precipitates a cascade of nucleotide catabolism. The clinical syndrome of accelerated purine ribonucleotides catabolism, as defined by hyperuricemia, hyperuricosuria and elevated urinary oxypurines, has primary and secondary causes. Treatment of these disorders is in general directed toward reversal of the precipitating factors, inhibition of further nucleotide degradation, and stimulation of purine nucleotide and ATP formation. Careful clinical application of these principles seems indicated.

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An allosteric and a non-allosteric guanine deaminase isozyme in rat liver supernatant

Kumar

Krishnan

1970

Biochemical and Biophysical Research Communications

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Regulation of rat liver guanine amino hydrolase by GTP

Cited by 8 publications

References 4 publications

Guanine deaminase in rat liver and mouse liver and brain

Guanine deaminase in rat liver and mouse liver and brain

Purine Ribonucleotide Catabolism: Clinical and Biochemical Significance

An allosteric and a non-allosteric guanine deaminase isozyme in rat liver supernatant

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